<style>
div {
    position: relative;
    height: 100px;
    width: 100px;
    background: blue;
}
</style>

Animation with endDelay on and off the compositor. The two boxes should have identical motions.
<br>

<div id="target1"></div>
<div id="target2"></div>

<script>
var player1 = target1.animate([
  {left: '0px'},
  {left: '400px'},
], {
  duration: 1000,
  endDelay: -500,
});

var player2 = target2.animate([
  {transform: 'translate(0px)'},
  {transform: 'translate(400px)'},
], {
  duration: 1000,
  endDelay: -500,
});
</script>
